1. Field of the Invention
This invention relates to an agricultural planting implement and, more particularly, to a planting implement which is operable to plant row crops such as corn and which is further operable to operate as a grain drill to plant narrow spaced crops such as soybean, wheat and oats.
2. Description of the Prior Art
Two types of seeding machinery commonly used by modern farmers are row crop planters and grain drills, both of which are adapted to place seeds in rows. The row crop planter is typically used for planting crops in rows with spacings of 30 to 40 inches such that the crops may be easily cultivated to control weeds. The spacing provided by row crop planters also facilitates the harvesting of such crops as corn and sorghum which are most effectively harvested by machine when in widely spaced rows.
A commonly used row crop planter includes a plurality of planter units which are attached to a tool bar wherein the planter units each include a furrow opener, a seed metering and placement system, a seed depth control and a seed covering and packing device. The operation of the row crop planter is characterized by providing accurate depth control of the seeds placed within the furrows and by providing accurate individual seed placement, or singulation, whereby the crop yield is maximized by precisely positioning the seeds in spaced relationship to each other in the rows. The furrow depth is typically controlled by a double disk furrow opener having a gauge wheel located on either side thereof wherein the gauge wheels follow the contour of the soil to ensure that a substantially uniform furrow depth is formed. In addition, each planter unit is typically mounted for vertical movement relative to the tool bar to facilitate operation of the furrow opener and gauge wheels in producing a uniform furrow depth.
As noted above, a drill provides a narrower row spacing for crops such as soybean, wheat and oats wherein the rows are typically spaced approximately 7 to 10 inches apart. In order to obtain the narrow spacing between rows, the construction of a drill typically comprises a plurality of closely spaced furrow openers and depth control means, such as a pair of narrow gauge wheels or a single wide gauge wheel, adjacent to the openers. The narrow spacing between the rows dictates a narrow total width for the gauge wheel (or wheels) associated with each furrow opener, as compared to the total gauge wheel width for each planter unit of a row crop planter, resulting in a less accurate seed placement depth for drill planted seed.
Drills also typically include relatively lengthy feed tubes extending from a seed supply and metering area of the drill to the furrow opener. The lengthy feed tubes are necessitated by the close spacing between rows which prevents positioning of metering units, which may be relatively wide, in close proximity to the furrow openers. As a result of conveying seeds through the lengthy feed tubes, seeds commonly become grouped together as they travel through the tubes such that seed singulation is difficult or impossible to assure in a drill.
In addition, the space limitations of a drill usually prevent a coulter blade from being mounted to the individual planter units for preventing accumulation of trash at the furrow opener. In contrast, row crop planters are commonly provided with a coulter blade associated with each planter unit wherein the coulter blades cut through trash or crop residue in untilled land to facilitate use of the row crop planter in an untilled soil condition.
It is further known to provide an additional gang of planter units attached to the rear of a conventional row crop planter in order to provide an extra row between each row of seeds planted by the row crop planter. However, while such a set-up increases the number of rows planted, the minimum row spacing obtained by this arrangement is approximately 15 inches and it is desirable to obtain row spacings at least as low as 10 inches in order to maximize the yield from a given plot of land.
Therefore, there is a need for a planting implement which provides the advantages of accurate depth control and precise seed metering associated with a row crop planter, and which provides narrow row crop spacing whereby the advantages of drill planting are obtained.